The invention relates to a metallic flat gasket, particularly a cylinder head gasket, with a substantially flat gasket body having at least one beaded gasket plate, especially a cylinder head gasket having parallel sealing surfaces which surround at least one opening.
As the sealing gap between the head and the cylinder block of an internal combustion engine oscillates as a result of internal pressure and temperature fluctuations and consequently a sealing or gasket embodiment is subject to constant pressure changes, the gasket must have very good and durably resilience characteristics. As a result of the shaping of the beads an adequate elasticity is to be achieved, so as to ensure a permanent sealing of the different operating media.
To ensure the necessary elasticity on a long term basis, neither in the fitted state of the gasket, nor in the operating state with the various dynamic loads, must the beads be pressed completely flat.
It is known from the Applicant's German Published Application 38 35 611 to construct the bead with a smaller thickness than the gasket body and to taper it from said gasket body to its free edge. In the relieved state the bead projects with at least one convex bulge over the space defined by the two sealing surfaces.
It is also known to insert a thin metal sheet as an intermediate layer below the gasket plate and to fold it round in the vicinity of the beads. This leads to a projection level with the sheet metal thickness, which prevents the bead from being flattened. However, it is disadvantageous that the projection is of the same height as a result of the system in the case of all holes to be sealed, so that a desired, planned surface pressure matching is excluded, this being the prerequisite for sealing under differing constructional conditions. However, if an attempt was made to use different sheet metal thicknesses within a gasket body, this would prove uneconomic.